Legal API - BEN IA Shares Series Error

When clicking File and Pay this error comes up, however, the Shares step shows no error.

Desired behaviour/To Do List:

- [ ] A Class of shares and a Series inside that class are okay to share the same name.

- [ ] Update Unit Tests

This is based on this answer from the Business' Policy Analyst:
"Can a share series contain the same name as the share class?
Yes. There is nothing in the BCA or BCR that prohibits this naming convention. Additionally I went into test COLIN and tested out these naming conventions; while there cannot be multiple share series with the same name in the same class, nor multiple share classes with the same name, a share class and shares series under that class appears to be able to list the same name."

Existing behaviour:

- [ ] When invoking the "Review and Confirm" page, show that the Shares block has an error.




**Steps to Reproduce**
Steps to reproduce the behaviour:
1. Start a named BEN Incorporation Application
2. Enter a Shares class named Common
3. Add special restrictions to that class, so that you can add a series too
4. Add a series named Common
5. Observe that the Shares module validation does not complain
6. Observe that when clicking File and Pay the error comes up

Start with the Shares module validation and the Review and Confirm/File and Pay flow described in the reproduction steps. Trace why a class and its series may pass module validation but fail at filing, then update the unit tests. Done means matching class and series names are accepted consistently and the relevant validation state is shown in the Shares block.

Written by the indexing model from the issue text.